The isoenergetic-isochoric (specified internal energy-specified volume, UV) flash is required to simulate the dynamic filling of a process vessel. Unlike other types of flashes, such as the isenthalpic-isobaric or isothermal-constant phase fraction flash calculations, for example, none of the intensive variables (temperature T and pressure P) is known in the UV flash. This fact introduces a higher degree of difficulty in solving the particular flash calculation than that of the other types. In this paper, we will share our experience in solving the UV flash problem.